Antracites (or Antrachas or Anthrax)

Antracites (or Antrachas or Anthrax)
A stone, sparkling like fire and girdled with a white vein,
supposed by Albertus Magnus to be the carbuncle. It was said
to cure imposthumes (purulent swellings). If smeared with oil
it loses its color but sparkles the more for being dipped in
water.